METHOD FOR ADDITIVE MANUFACTURING USING A BUNDLED POWER SOURCE, IN WHICH THE METHOD IS CONTROLLED DEPENDING ON THE STRENGTH OF A CONTROL CURVE OF THE BUNDLED POWER SOURCE

Description

[0001] The present application relates to an additive manufacturing method using a focused energy source, said method being regulated according to the intensity of a control current of said focused energy source. More particularly, the invention relates to an additive manufacturing method by deposition of material under focused energy called DED for "Directed Energy Deposition" in English.

[0002] In the aeronautics industry, some titanium parts, such as the primary structure of a jet engine strut, are made by assembling several complex parts machined from blocks of material. This manufacturing technique is relatively time-consuming and generates a lot of material loss in the form of titanium shavings that cannot be reused. To reduce the amount of waste, additive manufacturing processes make it possible to create parts by stacking layers of material on top of each other.

[0003] Patent GB2452774 (describing the preamble of claim 1) provides a method of manufacturing a titanium alloy tube by melting a titanium alloy wire to make the tube layer by layer.

[0004] According to an embodiment illustrated by the figure 1 , a part 10 is produced by stacking layers of material 12 obtained by melting a material using a focused energy source, such as a laser beam, an electron beam for example. According to a technique called focused energy material deposition, the material in the form of powder or wire is deposited simultaneously with the energy input.

[0005] According to one operating method, a titanium wire is unwound as the focused energy source advances so as to obtain a superposition of material beads. During tests to manufacture titanium parts by material deposition under focused energy, a particular phenomenon of energy runaway, also called flash, occurs randomly and uncontrolled, causing the destruction of the titanium bead just deposited and the surrounding structure, as illustrated in the figure 2 .

[0006] While the energy levels per unit area used are of the order of 500 J / mm 2< to obtain a regular bead, the energy levels per unit area are between 3000 J / mm 2< and 8000 J / mm 2< at the time of an energy runaway, which leads to the destruction of the titanium bead and the surrounding structure as well as to the scrapping of the part.

[0007] Since this energy runaway remains a phenomenon that is difficult to control, this additive manufacturing technique by deposition of material under focused energy cannot be implemented in mass-produced part manufacturing processes.

[0008] The present invention aims to remedy all or part of the drawbacks of the prior art.

[0009] To this end, the invention relates to a method for manufacturing a part by stacking layers of material each obtained by continuously depositing and melting a material in an impact zone targeted by an energy beam as defined in claim 1.

[0010] This temporary shutdown of the manufacturing process when the control current intensity exceeds a given threshold significantly reduces the risk of energy runaway.

[0011] According to another characteristic, the manufacturing method comprises a step of resuming the manufacturing method when the intensity of the measured control current becomes lower than the given threshold.

[0012] According to another feature, during the recovery step, the focused energy source is switched to the activated state.

[0013] According to another feature, during the resumption step, the material feed system is switched to the activated state.

[0014] According to another characteristic, if the intensity of the monitored control current is greater than the given threshold, the manufacturing method comprises a step of deactivating the focused energy source during which the focused energy source is switched to the deactivated state, the focused energy source and the part being immobilized relative to each other as well as a step of deactivating the material feed system during which the material feed system is switched to the deactivated state, the material feed system and the part being immobilized relative to each other.

[0015] According to another feature, the steps of deactivating the focused energy source and the material supply system are carried out simultaneously.

[0016] According to another feature, the step of monitoring the intensity of the control current is carried out continuously.

[0017] According to another characteristic, the given threshold is equal to the operating intensity increased by a percentage corresponding to the operating intensity divided by 10. Other characteristics and advantages will emerge from the description of the invention which follows, a description given by way of example only, with reference to the appended drawings among which: There figure 1 is a representation of a part of a part obtained by an additive manufacturing process by deposition of material under focused energy without energy runaway, The figure 2 is a representation of a part of a part obtained by an additive manufacturing process by deposition of material under focused energy with an energy runaway, The figure 3 is a schematic representation illustrating a manufacturing device for implementing an additive manufacturing process by deposition of material under focused energy, and The figure 4 is a diagram illustrating an additive manufacturing process by deposition of material under focused energy illustrating an embodiment of the invention.

[0018] As illustrated in the figure 3 , an additive manufacturing process by deposition of material under focused energy makes it possible to obtain a part 14 by stacking layers of material 16 obtained by continuously depositing a material 18 and by fusing it using a focused energy source 20.

[0019] According to one operating mode, the focused energy source 20 generates an energy beam 22 having an impact point 22.1 in an impact zone 24 located on a substrate 26 and at which the material 18 is supplied in the form of at least one wire or powder. Generally, the impact zone 24 is located in a controlled atmosphere 28 having at least one controlled characteristic among the gas composition, the kinematics of the gases, the pressure, the temperature for example.

[0020] The substrate 26 may be a support independent of the part 14 to be produced or a layer of material 16 already deposited on the part 14.

[0021] The energy beam 22 may be a laser beam, an electron beam, a plasma beam or others.

[0022] According to one configuration, the layers of material 16 are cords of material.

[0023] A manufacturing device 30 for implementing the manufacturing method comprises, in addition to the focused energy source 20, a material supply system 32 configured to supply the impact zone 24 with material 18 at a supply point 32.1, an atmosphere management system 34 configured to manage at least one characteristic of the controlled atmosphere 28, at least one movement system 36 configured to move the substrate 26, the focused energy source 20 and / or the material supply system 32 as well as a control system 38 configured to control the focused energy source 20, the material supply system 32, the atmosphere management system 34 and each movement system 36.

[0024] The focused energy source 20 comprises a control 40 for controlling at least one characteristic of the energy beam 22. The control 40 is configured to control a control current having an intensity which makes it possible to control at least one characteristic of the energy beam 22. In the case of a focused energy source 20 and according to the invention, the control current corresponds to the electric supply current 40.1 of the focused energy source 20. According to one embodiment, the control 40 comprises a measuring device 40.2 for measuring the intensity of the electric supply current 40.1.

[0025] The focused energy source 20 is configured to occupy an activated state in which it generates the energy beam 22 and a deactivated state in which it does not generate the energy beam 22.

[0026] The material feed system 32 is configured to occupy an activated state in which it feeds the impact zone 24 with material 18 and a deactivated state in which it no longer feeds the impact zone 24 with material 18.

[0027] The atmosphere management system 34 is configured to occupy an activated state in which it regulates at least one characteristic of the controlled atmosphere 28 and a deactivated state in which it does not regulate any characteristic of the controlled atmosphere 28.

[0028] Each movement system 36 is configured to occupy an activated state in which it moves the focused energy source 20 and / or the material supply system 32 and a deactivated state in which the focused energy source 20 and the material supply system 32 are stationary.

[0029] According to one embodiment, the material 18 may be titanium or Inconel ®<. It is in the form of a wire. Of course, the invention is not limited to this embodiment for the material 18.

[0030] In one configuration, the manufacturing device 30 includes a single movement system 36 supporting the focused energy source 20 and the material feed system 32. In another configuration, the manufacturing device 30 includes a first movement system supporting the focused energy source 20 and a second movement system supporting the material feed system 32. In another configuration, the manufacturing device 30 includes a movement system configured to move the substrate 26.

[0031] During the manufacturing process, a large number of parameters must be controlled and commanded so that the deposited layer of material 16 exhibits at least one expected characteristic. The expected characteristics include in particular dimensional characteristics, mechanical characteristics, and health characteristics of the material.

[0032] Certain controlled and commanded parameters relate to the focused energy source 20, the energy beam 22 and the movement system 36 supporting the focused energy source 20. For information purposes, the parameters relating to the focused energy source 20, the energy beam 22 and the movement system 36 supporting the focused energy source 20 are the activated / deactivated state of the focused energy source 20, the position of the point of impact 22.1 of the energy beam 22, the speed of movement of the point of impact 22.1 of the energy beam 22, the power, energy, frequency and / or pulse of the energy beam 22 as well as the dimension of the point of impact 22.1. This list of parameters relating to the focused energy source 20, the energy beam 22 and the movement system 36 supporting the focused energy source 20 is not exhaustive.

[0033] Certain controlled and commanded parameters relate to the material 18, the material feed system 32 and the movement system 36 supporting the material feed system 32. For information purposes, the parameters relating to the material 18, the material feed system 32 and the movement system 36 supporting the material feed system 32 are the nature and properties of the material 18 used, the activated / deactivated state of the material feed system 32, the position of the feed point 32.1 as well as the movement speed of the feed point 32.1. This list of parameters relating to the material 18, the material feed system 32 and the movement system 36 supporting the material feed system 32 is not exhaustive.

[0034] Some other controlled and commanded parameters are related to the atmosphere management system 34.

[0035] According to one embodiment, the manufacturing device 30 comprises a plurality of sensors configured to measure or determine values ​​of certain characteristics relating to the focused energy source 20, to its control 40, to the energy beam 22, to the impact zone 24, to the controlled atmosphere 28, to the material supply system 32, to the atmosphere management system 34, to the displacement system(s) 36, the measured or determined values ​​being transmitted to the control system 38.

[0036] According to one operating mode, the control system 38 comprises at least one control law making it possible, from these measured or determined values, to control or command the focused energy source 20, the energy beam 22, the material supply system 32, the atmosphere management system 34, the movement system(s) 36.

[0037] Generally, the control system 38 comprises several control laws.

[0038] In operation, the energy level per unit area at the impact zone 24 is less than 3000 J / mm 2 < . Generally, this energy level per unit area is between 40 J / mm 2 < and 3000 J / mm 2 < .

[0039] If the energy level per unit area remains below a given threshold, the material layer 16 is correctly formed and has the expected characteristics.

[0040] In a random and unexplained manner, an energy runaway during which the energy per unit area is significantly greater than 3000 J / mm 2< and can reach values ​​close to 8000 J / mm 2<, can occur and disrupt the formation of the layer of material 16 which then no longer exhibits the expected characteristics.

[0041] During an energy runaway, certain controlled and commanded parameters diverge and become uncontrollable. Given the large number of parameters and their interactions, it is very difficult to determine which one plays a major role in this energy runaway phenomenon and what corrective action should be implemented.

[0042] According to the invention, the parameter controlled to avoid a runaway phenomenon is the intensity of the control current of the focused energy source 20 which must remain below a given threshold. The corrective measure to avoid energy runaway is stopping the process as long as the intensity of the control current of the focused energy source 20 is greater than the given threshold. The manufacturing process resumes when the intensity of the control current becomes lower than the given threshold.

[0043] According to a procedure illustrated on the figure 4, the manufacturing method comprises a step 42 of monitoring the intensity of the control current of the focused energy source 20 as well as a step 44 of comparing the intensity of the monitored control current with the given threshold.

[0044] This step 42 of monitoring the intensity of the control current can be carried out regardless of the activated or deactivated state of the focused energy source 20, of the material supply system 32 and / or of the displacement system(s) 36.

[0045] If the intensity of the monitored control current is lower than the given threshold, the manufacturing method comprises a continuation step 46 up to a final step 48 of obtaining the part 14.

[0046] If the intensity of the monitored control current is greater than the given threshold, the manufacturing method comprises a step 50 of deactivating the focused energy source 20 during which the focused energy source 20 is switched to the deactivated state, the focused energy source 20 and the part 14 being immobilized relative to each other as well as a step 52 of deactivating the material supply system 32 during which the material supply system 32 is switched to the deactivated state, the material supply system 32 and the part 14 being immobilized relative to each other, then a step 54 of resuming the method when the intensity of the monitored control current becomes lower than the given threshold.

[0047] According to one embodiment, the steps 50, 52 of deactivating the focused energy source 20 and the material supply system 32 are carried out simultaneously.

[0048] In the resumption step 54, the focused energy source 20, the material supply system 32 and each movement system 36 are switched to the activated state.

[0049] This temporary shutdown of the manufacturing process when the control current intensity exceeds a given threshold significantly reduces the risk of energy runaway.

[0050] According to one operating mode, the step of monitoring the intensity of the control current is carried out continuously.

[0051] According to the invention, the given threshold is a function of an operating intensity which corresponds to the intensity of the control current used during the manufacturing process without energy runaway. Depending on the manufacturing methods, this operating intensity is for example between 50 and 300 mA.

[0052] According to one embodiment, the given threshold is equal to the operating intensity increased by a percentage corresponding to the operating intensity divided by 10. Thus for an operating intensity of the order of 50 mA, the threshold is equal to 50 + 5%, or 52.5 mA. For an operating intensity of the order of 300 mA, the threshold is equal to 300 + 30%, or 390 mA.

Claims

1. Method for manufacturing a component (14) by stacking layers of material (16) that are each obtained by depositing and melting, continuously, a material (18) in an impact zone (24) targeted by an energy beam (22), the material (18) coming from a material supply system (32) configured to occupy an activated state in which the material supply system (32) supplies the impact zone (24) with material (18) and a deactivated state in which the material supply system (32) no longer supplies the impact zone (24) with material (18), the energy beam (22) being emitted by a focused energy source (20) configured to occupy an activated state in which the focused energy source (20) generates the energy beam (22) and a deactivated state in which it does not generate the energy beam (22), the energy beam (22) having at least one feature controlled by a control current intensity which corresponds to the supply electric current (40.1) of the focused energy source (20), wherein the manufacturing method comprises a step (42) of monitoring the control current intensity, a step (44) of comparing the monitored control current intensity with a given threshold which is a function of an operating intensity corresponding to the intensity of the control current used during the manufacturing process without energy runaway and a step of stopping the manufacturing method when the control current intensity is above the given threshold.

2. Method for manufacturing as claimed in the preceding claim, wherein the manufacturing method comprises a resumption step (54) of the manufacturing method when the measured control current intensity falls back below the given threshold.

3. Method for manufacturing as claimed in the preceding claim, wherein, during the resumption step (54), the focused energy source (20) is switched to the activated state.

4. Method for manufacturing as claimed in claim 2 or 3, wherein, during the resumption step (54), the material supply system (32) is switched to the activated state.

5. Method for manufacturing as claimed in one of the preceding claims, wherein, if the monitored control current intensity is above the given threshold, the manufacturing method comprises a step (50) of deactivating the focused energy source (20) during which the focused energy source (20) is switched to the deactivated state, the focused energy source (20) and the component (14) being immobilized with respect to one another, and a step (52) of deactivating the material supply system (32) during which the material supply system (32) is switched to the deactivated state, the material supply system (32) and the component (14) being immobilized with respect to one another.

6. Method for manufacturing as claimed in the preceding claim, wherein the steps (50, 52) of deactivating the focused energy source (20) and the material supply system (32) are carried out simultaneously.

7. Method for manufacturing as claimed in one of the preceding claims, wherein the step of monitoring the control current intensity is carried out continuously.

8. Method for manufacturing as claimed in one of the preceding claims, wherein the given threshold is equal to the operating intensity increased by a percentage corresponding to the operating intensity divided by 10.